9 February 2011 Optimisation of pattern geometry and investigations of physical mechanisms contributing to improved light extraction in patterned substrate LEDs
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Abstract
In this paper we investigate the use of a patterned layer placed at the substrate / GaN interface region of a p-side up LED to improve light extraction and investigate the optimization of performance geometry by adjustment of geometrical parameters associated with the shaped structures including: side wall angle, side wall curvature, height and lattice constant. Performance is in each case evaluated in terms of angular extraction efficiency and far field angular beam profile. Comparisons are made between conventional large pitch patterned substrate (PSS) designs which have multiple wavelength length scales, and photonic crystal lattices which have a (sub) wavelength length scale. Physical mechanisms giving rise to the improvements are identified and discussed in each case. Overall a maximum improvement in extraction efficiency of 66% was obtained for a 4500nm pitch lattice of truncated cones.
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Martin D. B. Charlton, Martin D. B. Charlton, Sean Linn, Sean Linn, } "Optimisation of pattern geometry and investigations of physical mechanisms contributing to improved light extraction in patterned substrate LEDs", Proc. SPIE 7954, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XV, 795419 (9 February 2011); doi: 10.1117/12.874187; https://doi.org/10.1117/12.874187
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